Working with CSV files - powershell

Question

Suppose I have a table like this in data.csv:
time channel x y z
0.001 point 1 1 2 3
0.001 point 2 4 5 6
0.001 point 3 7 8 9
0.001 point 4 10 11 12
0.001 point 5 13 14 15
0.002 point 1 2 3 4
0.002 point 2 5 6 7
0.002 point 3 8 9 10
0.002 point 4 11 12 13
0.002 point 5 14 15 16
0.004 point 1 3 4 5
0.004 point 2 6 7 8
0.004 point 3 9 10 11
0.004 point 4 12 13 14
0.004 point 5 15 16 17
How do I make Powershell to write out 3 files (Xdata.csv, Ydata.csv, Zdata.csv), which Xdata.csv should look like this:
time point 1 point 2 point 3 point 4 point 5
0.001 1 4 7 10 13
0.002 2 5 8 11 14
0.004 3 6 9 12 15
So far, my code looks like this:
# Path to current directory
$path = [System.IO.Path]::GetDirectoryName($myInvocation.MyCommand.Definition)
# csv filename to be imported from
$filename = "data.csv"
$data = Import-Csv "$path\$filename"
# Array of unique values of times
$times = $data | % { $_.time } | Sort-Object | Get-Unique
# Array of unique values of channels
$channels = $data | % { $_.channel } | Sort-Object | Get-Unique
But at this point, I am struggling of how to set up an output table just like the one above.

Answer 1

I would use Group-Object + some logic to generate objects using data from each 'time' snapshot
$collections = #{
x = #()
y = #()
z = #()
}
$data | Group time | ForEach-Object {
$x = New-Object PSObject -Property #{
time = $_.Name
}
$y = New-Object PSObject -Property #{
time = $_.Name
}
$z = New-Object PSObject -Property #{
time = $_.Name
}
foreach ($item in $_.Group) {
if ($item.channel) {
$x | Add-Member -MemberType NoteProperty -Name $item.channel -Value $item.x
$y | Add-Member -MemberType NoteProperty -Name $item.channel -Value $item.y
$z | Add-Member -MemberType NoteProperty -Name $item.channel -Value $item.z
}
}
$collections.x += $x
$collections.y += $y
$collections.z += $z
}
foreach ($coordinate in 'x','y','z') {
$collections.$coordinate | Export-Csv -NoTypeInformation "${coordinate}data.csv"
}
This is with assumption that 'data' contains object similar to one I could generate with:
New-Object PSObject -Property #{
time = 0.001
channel = 'point 1'
x = 1
y = 2
z = 3
}

Answer 2

More of a pipeline approach (not tested)
$axes = #{
x = [ordered]#{}
y = [ordered]#{}
z = [ordered]#{}
}
import-csv data.csv |
foreach-object {
if ( $axes.x.containskey($_.time) )
{
foreach ($axis in 'x','y','z')
{ $axes.$axis[$_.time].add($_.channel,$_.$axis) }
}
else {
foreach ($axis in 'x','y','z')
{ $axes.$axis[$_.time] = [ordered]#{ time = $_.time;$_.channel = $_.$axis } }
}
}
foreach ($axis in 'x','y','z')
{
$(foreach ($time in $axes.$axis.values)
{ [PSCustomObject]$time })|
export-csv ${$axis}data.csv -NoTypeInformation
}